Battery cell, battery pack and automobile including the same

Abstract

A battery cell according to one embodiment of the present invention includes an electrode assembly including a first electrode, a second electrode, and a separator interposed therebetween; a battery housing that receives the electrode assembly through an opening formed on one side; and a housing cover that covers the opening and has a vent configured to rupture when internal pressure of the battery housing increases above a certain level, wherein the vent includes an upper notch provided on an upper surface of the housing cover and a lower notch provided on a lower surface of the housing cover, and the upper notch and the lower notch are offset from each other.

Description

[Technical Field]

[0001] The present invention relates to a battery cell, a battery pack, and a vehicle including the same.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0157708, filed on November 22, 2022, and the entire contents disclosed in the specification and drawings of that application are incorporated herein by reference. [Background technology]

[0003] Secondary batteries, which have high applicability to various products and electrical properties such as high energy density, are widely used not only in portable devices but also in electric vehicles (EVs) and hybrid electric vehicles (HEVs), which are powered by electrical sources. These secondary batteries are attracting attention as a new energy source that is environmentally friendly and improves energy efficiency because they do not produce any by-products associated with energy use, in addition to their primary advantage of dramatically reducing the use of fossil fuels.

[0004] Currently, widely used types of secondary batteries include lithium-ion batteries, lithium polymer batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and nickel-zinc batteries. The operating voltage of such unit secondary battery cells, i.e., unit battery cells, is approximately 2.5V to 4.5V. Therefore, if a higher output voltage is required, a battery pack is constructed by connecting multiple battery cells in series. Alternatively, a battery pack can be constructed by connecting multiple battery cells in parallel depending on the required charge / discharge capacity of the battery pack. Therefore, the number of battery cells included in the battery pack can be variously set depending on the required output voltage or charge / discharge capacity.

[0005] Meanwhile, a battery cell may include a battery can and a cap covering one cross section of the battery can. In this case, the cap may have a vent formed to prevent an increase in internal pressure due to gas generated inside the battery can. However, in conventional battery cells, a large amount of material is required during notch forming to ensure a certain level of vent pressure, which increases the likelihood of mold damage. Therefore, it is necessary to reduce mold damage during notch forming and improve mold lifespan. Furthermore, there is a problem of reduced productivity due to the large amount of material required during notch forming. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to efficiently ensure vent pressure even when the amount of notch formation is small when forming a notch in a vent portion of a battery cell.

[0007] Another object of the present invention is to increase and improve the lifespan of a battery cell by reducing damage to a mold when forming a notch in a vent portion of the battery cell.

[0008] A further object of the present invention is to increase productivity by reducing the amount of notch formation.

[0009] However, the technical problems that the present invention aims to solve are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description of the invention. [Means for solving the problem]

[0010] To achieve the above object, a battery cell according to one embodiment of the present invention includes: an electrode assembly including a first electrode, a second electrode, and a separator interposed therebetween; a battery housing that receives the electrode assembly through an opening formed on one side; and a housing cover that covers the opening and has a vent configured to rupture when internal pressure of the battery housing increases above a certain level, wherein the vent includes an upper notch provided on an upper surface of the housing cover and a lower notch provided on a lower surface of the housing cover, and the upper notch and the lower notch are offset from each other.

[0011] Preferably, the vent portion is configured to form a circular closed loop.

[0012] In one aspect of the present invention, the center line of the upper notch portion and the center line of the lower notch portion may be spaced apart from each other by a predetermined distance in the radial direction.

[0013] Preferably, the upper notch portion may be provided radially inward of the lower notch portion.

[0014] In another aspect of the present invention, the upper notch portion and the lower notch portion may be configured to have a width that narrows as it moves inward from the surface of the housing cover.

[0015] In yet another aspect of the present invention, the upper notch portion may have an axisymmetric structure having a slope based on a center line of the upper notch portion, and the lower notch portion may have an axisymmetric structure having a slope based on a center line of the lower notch portion.

[0016] In one aspect of the present invention, a first line can be defined as an imaginary line passing through the shortest distance between the upper notch portion and the lower notch portion in a vertical cross section passing through the center of the housing cover, and a second line can be defined as an imaginary line perpendicular to the first line.

[0017] In this case, the angle formed between the second straight line and the surface of the housing cover may be greater than 0° and less than 90°.

[0018] In one aspect of the present invention, when the width of the entrance of the upper notch portion is W1 and the width of the entrance of the lower notch portion is W2, the distance between the center line of the upper notch portion and the center line of the lower notch portion can satisfy the following formula (1):

[0019]

number

[0020] In another aspect of the present invention, the upper notch portion and the lower notch portion may be configured to be point-symmetrical with each other in a vertical cross section passing through the center of the housing cover.

[0021] In yet another aspect of the present invention, the shortest distance between the upper notch portion and the lower notch portion in a vertical cross section passing through the center of the housing cover can be configured to be greater than the shortest distance between the upper notch portion and the lower notch portion when the upper notch portion and the lower notch portion are provided at the same radial position.

[0022] In yet another aspect of the present invention, the shortest distance between the upper notch portion and the lower notch portion in a vertical cross section passing through the center of the housing cover may be configured to be shorter than the thickness of the housing cover.

[0023] In yet another aspect of the present invention, the region in which the upper notch portion is formed and the region in which the lower notch portion is formed may be configured to at least partially overlap along a direction perpendicular to the housing cover.

[0024] In yet another aspect of the present invention, the shortest distance between the upper notch portion and the lower notch portion may be more than 10% of the thickness of the housing cover.

[0025] Furthermore, one aspect of the present invention provides a battery pack including at least one battery cell according to the above-described embodiment.

[0026] Another aspect of the present invention provides a vehicle, the vehicle including at least one battery pack according to the above-described embodiments. [Effects of the Invention]

[0027] According to one aspect of the present invention, even with a small amount of notch formation, it is possible to ensure a constant level of vent pressure in the battery cell.

[0028] Furthermore, according to another aspect of the present invention, damage to the mold is reduced due to a small amount of notch formation, and an increase in the lifespan of the battery cell can be expected.

[0029] In accordance with yet another aspect of the present invention, productivity is increased by reducing the amount of notch formation required.

[0030] The effects of the present invention are not limited to those described above, and other effects of the present invention not mentioned will be clearly understood by those skilled in the art from the following description of the invention.

[0031] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to further understand the technical concept of the present invention, so the present invention should not be interpreted as being limited to the matters described in the drawings. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a diagram illustrating a battery cell according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view of a vertical section of FIG. 1. [Figure 3] FIG. 2 is a longitudinal cross-sectional view of the battery cell of FIG. 1. [Figure 4] 10A and 10B are diagrams illustrating a housing cover according to an embodiment of the present invention. [Figure 5] 10A and 10B are diagrams illustrating a housing cover according to a comparative example of the present invention. [Figure 6]10A and 10B are diagrams illustrating a housing cover according to an embodiment of the present invention. [Figure 7] 10A and 10B are views illustrating a housing cover according to another embodiment of the present invention. [Figure 8] 10A and 10B are diagrams illustrating a vent portion according to an embodiment of the present invention. [Figure 9] 10A and 10B are diagrams illustrating the process of breaking a vent portion in a comparative example of the present invention. [Figure 10] 10A to 10C are diagrams illustrating a breaking process of a vent portion according to an embodiment of the present invention. [Figure 11] 1 is a diagram illustrating a battery pack including a battery cell according to an embodiment of the present invention; [Figure 12] FIG. 12 is a diagram illustrating a vehicle including the battery pack of FIG. 11. DETAILED DESCRIPTION OF THE INVENTION

[0033] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed as meanings and concepts corresponding to the technical ideas of the present invention, based on the principle that the inventor himself can appropriately define the concepts of terms in order to best explain the invention. Therefore, it should be understood that the embodiment described in this specification and the configurations shown in the drawings are merely the most preferred embodiment of the present invention and do not represent the entire technical ideas of the present invention, and therefore various equivalents and modifications that can be substituted therefor may exist at the time of filing this application.

[0034] In addition, in order to facilitate understanding of the invention, the accompanying drawings may be drawn not to scale but with some components exaggerated. The same reference numerals may be used to refer to the same components in different embodiments.

[0035] When two comparison objects are identical, it means that they are "substantially identical." Therefore, "substantially identical" may include deviations that are considered low in the art, for example, deviations within 5%. Furthermore, when any parameter is uniform in a given region, it may mean uniformity on average.

[0036] Terms such as "first" and "second" are used to describe various components, but these terms are not intended to limit the components. These terms are used to distinguish only one component from another, and unless otherwise specified, the first component may be the second component.

[0037] Furthermore, throughout the specification, unless otherwise specified, each element may be singular or plural.

[0038] When any structure is placed "on top (or bottom)" of a component or "above (or below)" a component, it can mean that the structure is placed directly on the top (or bottom) surface of the component, but also that other structures may be interposed between the component and any structure placed above (or below) the component.

[0039] Furthermore, when a component is described as being "coupled," "coupled," or "connected" to another component, it should be understood that the components may be directly coupled or connected to each other, but that other components may be "intervening" between the components, or that each component may be "coupled," "coupled," or "connected" by other components.

[0040] Throughout the specification, unless otherwise specified, "A and / or B" means "A," "B," or "A and B," and "C through D" means at least C and at most D, unless otherwise specified.

[0041] For ease of explanation, in this specification, the direction along the longitudinal direction of the winding shaft of the electrode assembly 10 wound in a jelly roll shape is referred to as the axial direction (Y direction). The direction surrounding the winding shaft is referred to as the circumferential direction or circumferential direction (X direction). The direction approaching the winding shaft and moving away from the winding shaft is referred to as the radial direction. Of these, the direction approaching the winding shaft is particularly referred to as the mesial direction, and the direction moving away from the winding shaft is particularly referred to as the centrifugal direction.

[0042] Fig. 1 is a diagram illustrating a battery cell 1 according to an embodiment of the present invention, and Fig. 2 is a perspective view of a vertical cross section of Fig. 1. Fig. 3 is a vertical cross section of the battery cell 1 of Fig. 1.

[0043] 1, a battery cell 1 according to an embodiment of the present invention includes an electrode assembly 10, a battery housing 20, and a housing cover 30. The battery cell 1 may further include a current collector 40. The present invention is not limited by the shape of the battery and may also be applied to batteries of other shapes, for example, prismatic batteries.

[0044] 2 and 3, the electrode assembly 10 includes a first electrode tab 11 and a second electrode tab 12. Specifically, the electrode assembly 10 includes a first electrode, a second electrode, and a separator interposed therebetween. The electrode assembly 10 has a structure in which the first electrode, the second electrode, and the separator interposed therebetween are wound around a winding shaft, with the separator interposed therebetween, thereby defining a core and an outer circumferential surface. That is, the electrode assembly 10 applicable to the present invention may be a jelly-roll type electrode assembly 10. In this case, a separator may be further provided on the outer circumferential surface of the electrode assembly 10 for insulation from the battery housing 20. The electrode assembly 10 may be wound using any winding structure known in the art without limitation.

[0045] Meanwhile, in the present invention, the positive electrode active material coated on the positive electrode plate and the negative electrode active material coated on the negative electrode plate may be any active material known in the art without any limitations.

[0046] 1 and 2, the battery housing 20 is a generally cylindrical container having an opening on one side and is made of a conductive metal material. The side surface of the battery housing 20 and the bottom surface opposite the opening are typically integrally formed. That is, the battery housing 20 typically has an open top end in its height direction and a closed bottom end. The bottom surface of the battery housing 20 may be substantially flat. The battery housing 20 receives the electrode assembly 10 through an opening formed on one side in its height direction. The battery housing 20 may also receive an electrolyte through the opening.

[0047] The battery housing 20 may include a beading portion 21 formed at an end adjacent to an opening formed at an upper end of the battery housing 20. The battery housing 20 may further include a crimping portion 22 formed on the beading portion 21. The beading portion 21 has a shape in which the outer periphery of the battery housing 20 is pressed to a predetermined depth. More specifically, the beading portion 21 may have a shape in which the beading portion 21 is pressed inward in a region between an opening formed on one side of the battery housing 20 and a receiving portion that receives the electrode assembly 10.

[0048] The beading portion 21 is formed on the upper portion of the electrode assembly 10. The inner diameter of the battery housing 20 in the area where the beading portion 21 is formed is smaller than the diameter of the electrode assembly 10.

[0049] The beading portion 21 provides a support surface on which the housing cover 30 is mounted. The beading portion 21 may also provide a support surface on which at least a portion of the peripheral edge of the current collector 40 is mounted and coupled. That is, at least a portion of the peripheral edge of the current collector 40 and / or the peripheral edge of the housing cover 30 may be mounted on the upper surface of the beading portion 21. In order to stably support at least a portion of the peripheral edge of the current collector 40 and / or the peripheral edge of the housing cover 30, the upper surface of the beading portion 21 may extend in a direction substantially aligned with the lower surface of the battery housing 20, i.e., in a direction substantially perpendicular to the sidewall of the battery housing 20.

[0050] The beading portion 21 prevents the electrode assembly 10, which has a size approximately corresponding to the inner diameter of the battery housing 20, from slipping out of the opening formed at the upper end of the battery housing 20, and may function as a support portion on which the housing cover 30 is mounted. The upper beading portion 21 may function as a support portion for fixing not only the housing cover 30 but also the current collector 40, the sealing gasket G1, etc.

[0051] The crimping portion 22 is formed on the beading portion 21. The crimping portion 22 is bent and extends to surround the periphery of the housing cover 30 disposed on the beading portion 21. Due to the shape of the crimping portion 22, the housing cover 30 is fixed onto the beading portion 21.

[0052] 1 to 3, the housing cover 30 may include a vent portion 31 formed to prevent an increase in internal pressure due to gas generated inside the battery housing 20. The vent portion 31 may be configured to rupture when the internal pressure of the battery housing 20 increases above a certain level. For example, the vent portion 31 may be formed in a portion of the housing cover 30 and may be a region structurally weaker than the surrounding region so as to be easily ruptured when internal pressure is applied. The vent portion 31 may be, for example, a region thinner than the surrounding region.

[0053] That is, a thermal event may occur inside the battery cell 1 for any reason, generating vent gas, which may increase the internal pressure of the battery housing 20. In this case, the vent portion 31 is structurally weaker than the surrounding area so that it may easily rupture when the internal pressure of the battery cell 1 increases, and therefore, when vent gas is generated, rupture may occur at the vent portion 31.

[0054] 1 to 3, the housing cover 30 covers the opening formed on one side of the battery housing 20. The housing cover 30 may be fixed by a crimping portion 22 formed on the upper end of the battery housing 20. In this case, to improve fixing strength and sealing performance of the battery housing 20, a sealing gasket G1 may be interposed between the battery housing 20 and the housing cover 30 and between the current collector 40 and the housing cover 30. In this case, the contact portion 33a and / or the second contact portion may be interposed between the beading portion 21 of the battery housing 20 and the sealing gasket G1. In this manner, the contact portion 33a and / or the second contact portion interposed between the beading portion 21 and the sealing gasket G1 may be fixed by bending the crimping portion 22 extending upward from the beading portion 21.

[0055] Meanwhile, in the present invention, the housing cover 30 does not necessarily function as a current path. If the battery housing 20 and the housing cover 30 can be firmly fixed together by welding or by applying other parts, and the sealing of the open portion of the battery housing 20 can be ensured, the application of such a sealing gasket G1 is not essential.

[0056] Fig. 4 is a diagram illustrating a housing cover 30 according to an embodiment of the present invention, Fig. 5 is a diagram illustrating a housing cover 30 of a comparative example of the present invention, and Fig. 6 is a diagram illustrating a housing cover 30 according to an embodiment of the present invention.

[0057] 4 and 6, the vent portion 31 may include an upper notch portion N1 provided on the upper surface of the housing cover 30 and a lower notch portion N2 provided on the lower surface of the housing cover 30. Here, the upper notch portion N1 and the lower notch portion N2 may be offset from each other.

[0058] According to this structure, the upper notch portion N1 and the lower notch portion N2 are provided offset from each other, so that the stress applied to the region between the upper notch portion N1 and the lower notch portion N2 may be predominantly shear stress.

[0059] If the upper notch portion N1 and the lower notch portion N2 are aligned on the same line, as in the conventional housing cover 30 shown in FIG. 5, the stress applied to the region between the upper notch portion N1 and the lower notch portion N2 may be predominantly tensile. If the same amount of pressure is applied to the region between the upper notch portion N1 and the lower notch portion N2, as in FIG. 5 or FIG. 6, fracture is more likely to occur when shear stress is applied than when tensile stress is applied. Therefore, according to the present invention, fracture of the vent portion 31 is possible even when subjected to a lower vent pressure. Alternatively, by offsetting the upper notch portion N1 and the lower notch portion N2 from each other, the same vent pressure can be achieved with a smaller notch molding volume. Therefore, the reduced molding volume reduces mold damage, thereby extending the life of the housing cover 30.

[0060] 1 to 4, the vent portion 31 may be configured to form a substantially circular closed loop. As a result, when vent gas is ejected from inside the battery cell 1 and the housing cover 30 receives internal pressure upward, the vent portion 31 is ruptured, and the inner region of the circular closed loop of the housing cover 30 is ruptured. This allows smooth venting.

[0061] FIG. 7 is a diagram illustrating a housing cover 30 according to another embodiment of the present invention.

[0062] In one aspect of the present invention, the center line of the upper notch portion N1 and the center line of the lower notch portion N2 may be configured to be spaced apart by a predetermined distance in the radial direction. Here, the center line refers to a line that extends along the height direction of the battery cell 1 and passes through the center of the notch portions N1 and N2 in the width direction.

[0063] For example, referring to Fig. 6, the upper notch portion N1 may be provided radially inward from the lower notch portion N2. In another embodiment of the present invention, referring to Fig. 7, the upper notch portion N1 may be provided radially outward from the lower notch portion N2.

[0064] In this manner, with a structure in which the center line of the upper notch portion N1 and the center line of the lower notch portion N2 are radially spaced a predetermined distance apart, shear stress may be dominant in the stress applied to the region between the upper notch portion N1 and the lower notch portion N2. Therefore, according to the present invention, the vent portion 31 can be broken even under lower vent pressure. Alternatively, if the upper notch portion N1 and the lower notch portion N2 are misaligned, the same vent pressure may be achieved with a smaller notch molding volume. Therefore, the reduced molding volume reduces mold damage, thereby extending the life of the housing cover 30.

[0065] In another aspect of the present invention, the upper notch portion N1 and the lower notch portion N2 may be configured to have a width that narrows from the surface of the housing cover 30 toward the inside.

[0066] 6 or 7, the upper notch portion N1 and the lower notch portion N2 may be configured to have a substantially V-shaped cross section. Alternatively, in another embodiment, the upper notch portion N1 and the lower notch portion N2 may be configured to have a substantially U-shaped cross section. That is, the cross sections of the notch portions N1 and N2 may be configured to have slopes on both sides.

[0067] With this structure, when the center line of the upper notch portion N1 and the center line of the lower notch portion N2 are separated by a predetermined distance in the radial direction, the stress applied to the region between the upper notch portion N1 and the lower notch portion N2 may be dominated by shear stress.

[0068] In contrast, if the cross sections of the notches N1 and N2 are rectangular, unlike the present invention, the region between the upper notch N1 and the lower notch N2 will have a vertical structure without tilting, even if the centerline of the upper notch N1 and the centerline of the lower notch N2 are separated by a predetermined distance in the radial direction. Therefore, in this case, the stress applied to the region between the upper notch N1 and the lower notch N2 will not be dominated by shear stress. As a result, the vent pressure required for rupture will be higher than in the present invention.

[0069] On the other hand, according to one aspect of the present invention, the region between the upper notch portion N1 and the lower notch portion N2 has an inclined structure, so that when the center line of the upper notch portion N1 and the center line of the lower notch portion N2 are separated by a predetermined distance in the radial direction, the stress applied to the region between the upper notch portion N1 and the lower notch portion N2 can be configured to be shear stress.

[0070] 6 or 7, the upper notch portion N1 may have an axisymmetric structure having a slope based on a center line of the upper notch portion N1, while the lower notch portion N2 may have an axisymmetric structure having a slope based on a center line of the lower notch portion N2.

[0071] In this structure, the region between the upper notch portion N1 and the lower notch portion N2 has a sloped structure, so when the center line of the upper notch portion N1 and the center line of the lower notch portion N2 are spaced apart from each other by a predetermined distance in the radial direction, the stress applied to the region between the upper notch portion N1 and the lower notch portion N2 may be dominated by shear stress. Also, since the notches N1 and N2 have an axisymmetric structure with respect to the center line, the formation of the notches N1 and N2 may be facilitated in the process.

[0072] FIG. 8 is a diagram illustrating the vent portion 31 according to one embodiment of the present invention.

[0073] Referring to Figure 8, in a vertical cross section passing through the center of the housing cover 30, a first line SL can be defined as an imaginary line passing through the shortest distance D1 between the upper notch portion N1 and the lower notch portion N2, and a second line PL can be defined as an imaginary line perpendicular to the first line SL.

[0074] In this case, according to one aspect of the present invention, the angle formed between the second straight line PL and the surface of the housing cover 30 may be greater than 0° and less than 90°.

[0075] For example, as shown in FIG. 5, if the upper notch portion N1 and the lower notch portion N2 are aligned on the same line, the first line SL is perpendicular to the housing cover 30. Therefore, the second line PL is parallel to the housing cover 30, and the angle between the second line PL and the surface of the housing cover 30 is 0°. With this structure, the stress applied to the region between the upper notch portion N1 and the lower notch portion N2 becomes tensile stress, increasing the vent pressure required to break the vent portion 31. One way to reduce the vent pressure is to increase the size of the notch portion and reduce the thickness of the region between the upper notch portion N1 and the lower notch portion N2. However, this increases the molding volume and increases the likelihood of mold damage. This may shorten the lifespan of the housing cover 30. Therefore, it is preferable that the angle between the second line PL and the surface of the housing cover 30 be greater than 0°.

[0076] On the other hand, if the distance D2 between the center line of the upper notch portion N1 and the center line of the lower notch portion N2 is too large, the first line SL becomes almost parallel to the surface of the housing cover 30. As a result, the angle between the second line PL and the surface of the housing cover 30 becomes close to 90°. In such a case, the distance D2 between the upper notch portion N1 and the lower notch portion N2 becomes too large, which increases the thickness of the region between the upper notch portion N1 and the lower notch portion N2, thereby increasing the vent pressure required to break the vent portion 31. Therefore, it is desirable that the angle between the second line PL and the surface of the housing cover 30 be less than 90°.

[0077] As a result, it is more desirable that the angle between the second straight line PL and the surface of the housing cover 30 be 30° to 60°. When the angle is within the range of 30° to 60°, the thickness of the region between the upper notch portion N1 and the lower notch portion N2 is maintained at an appropriate level, and shear stress is applied to the region between the upper notch portion N1 and the lower notch portion N2. Therefore, according to this embodiment, the same vent pressure can be ensured even with a smaller notch molding amount. As a result, the reduced molding amount reduces mold damage, thereby extending the life of the housing cover 30.

[0078] In yet another aspect of the present invention, referring to FIG. 8, it is desirable that the distance D2 between the center line of the upper notch portion N1 and the center line of the lower notch portion N2 satisfy the following formula (1).

[0079]

number

[0080] Here, W1 means the width of the entrance of the upper notch portion N1, and W2 means the width of the entrance of the lower notch portion N2. In other words, the distance D2 between the center line of the upper notch portion N1 and the center line of the lower notch portion N2 is preferably smaller than the average value of the width W1 of the entrance of the upper notch portion N1 and the width W2 of the entrance of the lower notch portion N2, but larger than 0.

[0081] If the distance D2 between the center line of the upper notch portion N1 and the center line of the lower notch portion N2 is greater than the average of the width W1 of the inlet of the upper notch portion N1 and the width W2 of the inlet of the lower notch portion N2, the distance D2 between the upper notch portion N1 and the lower notch portion N2 will be excessively large, increasing the thickness of the region between the upper notch portion N1 and the lower notch portion N2, thereby increasing the vent pressure required to break the vent portion 31. On the other hand, if the distance D2 between the center line of the upper notch portion N1 and the center line of the lower notch portion N2 becomes zero, the upper notch portion N1 and the lower notch portion N2 will be aligned on the same line. As a result, the force predominantly applied to the vent portion 31 will be tensile stress. As a result, the vent pressure required to break the vent portion 31 will further increase. Therefore, only when the above formula (1) is satisfied can the same vent pressure be ensured with a smaller notch formation volume. As a result, damage to the mold is reduced due to the reduction in the molding amount, and the life of the housing cover 30 can be extended.

[0082] In yet another aspect of the present invention, the upper notch portion N1 and the lower notch portion N2 may be configured to be point-symmetrical with each other in a vertical cross section passing through the center of the housing cover 30.

[0083] 8, the upper notch portion N1 and the lower notch portion N2 may be configured to be point-symmetrical with respect to each other in a vertical cross section passing through the center of the housing cover 30, with respect to the intersection of the first line SL and the second line PL. That is, the shape of the upper notch portion N1 and the shape of the lower notch portion N2 may be substantially identical. With this structure, since the shapes of the notches N1 and N2 are inclined, shear stress may be applied to the region between the upper notch portion N1 and the lower notch portion N2.

[0084] In another aspect of the present invention, in a vertical cross section passing through the center of the housing cover 30, the shortest distance D1 between the upper notch portion N1 and the lower notch portion N2 can be configured to be larger than the shortest distance D1 between the upper notch portion N1 and the lower notch portion N2 when the upper notch portion N1 and the lower notch portion N2 are provided at the same radial position.

[0085] When the upper notch portion N1 and the lower notch portion N2 are aligned with each other as shown in FIG. 5, tensile stress is applied to the region between the upper notch portion N1 and the lower notch portion N2, increasing the vent pressure required to break the vent portion 31. Therefore, to reduce the vent pressure, the size of the notch portion must be increased to reduce the thickness of the region between the upper notch portion N1 and the lower notch portion N2. That is, the shortest distance D1 between the upper notch portion N1 and the lower notch portion N2 in a vertical cross section passing through the center of the housing cover 30 must be reduced. However, this increases the molding volume, increasing the likelihood of mold damage. This may shorten the lifespan of the housing cover 30.

[0086] On the other hand, in a structure in which the upper notch portion N1 and the lower notch portion N2 are offset from each other, as shown in Figure 8, shear stress is predominantly applied to the region between the upper notch portion N1 and the lower notch portion N2. Because fracture is more likely to occur when shear stress is applied than when tensile stress is applied under the same pressure, the same vent pressure can be ensured even with a smaller notch molding volume. That is, even if the shortest distance D1 between the upper notch portion N1 and the lower notch portion N2 in a vertical cross section passing through the center of the housing cover 30 is increased compared to the case of Figure 5, the same vent pressure can be ensured. As a result, damage to the mold is reduced due to the reduced molding volume, and the lifespan of the housing cover 30 can be extended.

[0087] In yet another aspect of the present invention, the shortest distance D1 between the upper notch portion N1 and the lower notch portion N2 in a vertical cross section passing through the center of the housing cover 30 can be configured to be shorter than the thickness of the housing cover 30.

[0088] 8, for example, the shortest distance D1 between the upper notch portion N1 and the lower notch portion N2 may be shorter than the thickness of the housing cover 30. Furthermore, the shortest distance D1 between the upper notch portion N1 and the lower notch portion N2 may be shorter than the widest width of the notch portions N1 and N2.

[0089] If the shortest distance D1 between the upper notch portion N1 and the lower notch portion N2 is configured too far, the thickness of the region between the upper notch portion N1 and the lower notch portion N2 increases, which increases the vent pressure required to break the vent portion 31. Therefore, it is desirable to maintain the shortest distance D1 between the upper notch portion N1 and the lower notch portion N2 at a certain distance or less.

[0090] In yet another aspect of the present invention, the region where the upper notch portion N1 is formed and the region where the lower notch portion N2 is formed may be configured to at least partially overlap in a direction perpendicular to the housing cover 30. For example, referring to FIGS. 6 and 7, the region where the upper notch portion N1 is formed and the region where the lower notch portion N2 is formed may be configured to at least partially overlap each other in a direction substantially perpendicular to the housing cover 30, i.e., the up-down direction in the drawings. This structure allows the minimum distance D1 between the upper notch portion N1 and the lower notch portion N2 to be set within a predetermined range. If the region where the upper notch portion N1 is formed and the region where the lower notch portion N2 is formed do not overlap each other in a direction substantially perpendicular to the housing cover 30, the minimum distance D1 between the upper notch portion N1 and the lower notch portion N2 may be excessively increased. This increases the thickness of the region between the upper notch portion N1 and the lower notch portion N2, thereby increasing the vent pressure required to break the vent portion 31. Therefore, it is desirable that the area in which the upper notch portion N1 is formed and the area in which the lower notch portion N2 is formed be configured to at least partially overlap each other along a direction approximately perpendicular to the housing cover 30.

[0091] In yet another aspect of the present invention, it is desirable that the shortest distance D1 between the upper notch portion N1 and the lower notch portion N2 exceeds 10% of the thickness of the housing cover 30.

[0092] For example, the vent pressure of a battery cell 1 of a particular design according to an embodiment of the present invention, including a housing cover 30 made of SUS430 and having a thickness of 0.7 mm, is approximately 17 kgf / cm. 2 To achieve this vent pressure, the minimum distance D1 between the upper notch portion N1 and the lower notch portion N2 needs to be approximately 0.070 mm, which is approximately 10% of the thickness of the housing cover 30. If the minimum distance D1 between the upper notch portion N1 and the lower notch portion N2 is less than this minimum distance, there is a high possibility that the mold will be damaged during molding, and the life of the housing cover 30 will be shortened. Therefore, it is desirable that the minimum distance D1 between the upper notch portion N1 and the lower notch portion N2 be more than 10% of the thickness of the housing cover 30.

[0093] FIG. 9 is a diagram illustrating the process of breaking vent portion 31 of a comparative example of the present invention, and FIG. 10 is a diagram illustrating the process of breaking vent portion 31 according to one embodiment of the present invention.

[0094] 9, in a conventional housing cover 30, the upper notch N1 and the lower notch N2 may be provided on the same line. In this case, the stress direction in the region between the upper notch N1 and the lower notch N2 is the direction of arrow A. In this case, tensile stress is predominantly applied in the direction A.

[0095] Meanwhile, referring to FIG. 10 , in a housing cover 30 according to one embodiment of the present invention, the upper notch portion N1 and the lower notch portion N2 are offset from each other, so the stress direction in the region between the upper notch portion N1 and the lower notch portion N2 is the direction of arrow B. In this case, shear stress is predominantly applied in the direction of B. Under the same pressure, fracture is more likely to occur when shear stress is applied than when tensile stress is applied. Therefore, according to the present invention, fracture of the vent portion 31 is possible even when subjected to a lower vent pressure. Furthermore, by offsetting the upper notch portion N1 and the lower notch portion N2 as in the present invention, the same vent pressure can be achieved with a smaller notch molding volume. As a result, the reduction in molding volume reduces mold damage and extends the life of the housing cover 30.

[0096] 1 and 2, a current collector 40 according to an embodiment of the present invention is housed inside a battery housing 20 and is electrically connected to the electrode assembly 10 and also to the battery housing 20. That is, the current collector 40 electrically connects the electrode assembly 10 and the battery housing 20.

[0097] 11, a battery pack 3 according to an embodiment of the present invention includes a battery assembly in which a plurality of battery cells 1 according to an embodiment of the present invention are electrically connected as described above, and a pack housing 2 that accommodates the battery assembly. For ease of illustration, components such as bus bars for electrical connections, a cooling unit, and power terminals are omitted from the drawings of the present invention. That is, the battery pack 3 may further include components of a battery pack known at the time of filing of the present invention, such as a BMS, a pack case, a relay, and a current sensor.

[0098] 12, an automobile 5 according to an embodiment of the present invention may be, for example, an electric automobile, a hybrid automobile, or a plug-in hybrid automobile, and may include a battery pack 3 according to an embodiment of the present invention. The automobile 5 includes a four-wheeled automobile and a two-wheeled automobile. The automobile 5 operates by receiving power from the battery pack 3 according to an embodiment of the present invention. In addition to the battery pack 3, the automobile 5 according to the present invention may further include various other components included in the automobile 5. For example, in addition to the battery pack 3 according to the present invention, the automobile 5 according to the present invention may further include a vehicle body, a motor, a control device such as an electronic control unit (ECU), and the like.

[0099] Although terms indicating directions such as "up" and "down" are used in this specification, it will be obvious to those skilled in the art that these terms indicate relative positions and are used merely for convenience of explanation, and may vary depending on the position of the object in question, the position of the observer, etc.

[0100] As described above, the present invention has been described using limited embodiments and drawings, but the present invention is not limited thereto, and it goes without saying that various modifications and variations can be made by a person having ordinary skill in the art to which the present invention pertains within the technical spirit of the present invention and the equivalent scope of the claims set forth below. [Explanation of symbols]

[0101] 5. Automobiles 3 Battery Pack 2-pack housing 1 battery cell 10 Electrode assembly 20 Battery housing 21 Beading section 22 Crimping section 30 Housing cover 31 Vent section N1 Upper notch N2 Lower notch G1 sealing gasket

Claims

1. an electrode assembly including a first electrode, a second electrode, and a separator interposed therebetween; a battery housing that receives the electrode assembly through an opening formed on one side thereof; a housing cover covering the opening and including a vent configured to rupture when the internal pressure of the battery housing increases above a certain level; the vent portion includes an upper notch portion provided on an upper surface of the housing cover and a lower notch portion provided on a lower surface of the housing cover, The battery cell, wherein the upper notch portion and the lower notch portion are offset from each other.

2. The battery cell according to claim 1 , wherein the vent portion forms a circular closed loop.

3. The battery cell according to claim 1 or 2, wherein a center line of the upper notch portion and a center line of the lower notch portion are spaced apart from each other by a predetermined distance in the radial direction.

4. The battery cell according to claim 1 or 2, wherein the upper notch portion is provided radially inward of the lower notch portion.

5. The upper notch portion and the lower notch portion are The battery cell according to claim 1 or 2, wherein the width of the housing cover narrows from the surface of the housing cover toward the inside.

6. 3. The battery cell according to claim 1, wherein the upper notch portion has an axisymmetric structure inclined with respect to a center line of the upper notch portion, and the lower notch portion has an axisymmetric structure inclined with respect to a center line of the lower notch portion.

7. In a vertical cross section passing through the center of the housing cover, a first line is defined as an imaginary line passing through the shortest distance between the upper notch portion and the lower notch portion, and a second line is defined as an imaginary line perpendicular to the first line. The battery cell according to claim 1 or 2, wherein an angle formed between the second straight line and a surface of the housing cover is greater than 0° and less than 90°.

8. When the width of the entrance of the upper notch portion is W1 and the width of the entrance of the lower notch portion is W2, The battery cell according to claim 1 or 2, wherein a distance D2 between a center line of the upper notch portion and a center line of the lower notch portion satisfies the following formula (1): [Equation 1]

9. The battery cell according to claim 1 or 2, wherein the upper notch portion and the lower notch portion are configured to be point-symmetrical with each other in a vertical cross section passing through a center of the housing cover.

10. 3. The battery cell according to claim 1, wherein a shortest distance between the upper notch portion and the lower notch portion in a vertical cross section passing through the center of the housing cover is greater than a shortest distance between the upper notch portion and the lower notch portion when the upper notch portion and the lower notch portion are provided at the same radial position.

11. The battery cell according to claim 1 or 2, wherein the shortest distance between the upper notch portion and the lower notch portion in a vertical cross section passing through the center of the housing cover is shorter than a thickness of the housing cover.

12. 3. The battery cell according to claim 1, wherein the region where the upper notch portion is formed and the region where the lower notch portion is formed at least partially overlap each other in a direction perpendicular to the housing cover.

13. The battery cell according to claim 1 or 2, wherein the shortest distance between the upper notch and the lower notch exceeds 10% of the thickness of the housing cover.

14. A battery pack comprising at least one battery cell according to claim 1 or 2.

15. A motor vehicle comprising at least one battery pack according to claim 14.

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